|Year of election|Candidates elected|# of seats available|# of votes|% of popular vote|
|---|---|---|---|---|
|1963|7|108|n.a.|15.5%|
|1967|20|117|n.a.|25.9%|
|1971|19|117|n.a.|27.1%|
|1975|38|125|n.a.|28.9%|
|1977|33|125|n.a.|28.0%|
|1981|21|125|n.a.|21.2%|
|1985|25|125|865,507|23.8%|
|1987|19|130|970,813|25.7%|
|1990|74|130|1,509,506|37.6%|
|1995|17|129|854,163|20.6%|
|1999|9|103|551,009|12.6%|
|2003|7|103|660,730|14.7%|
|2007|10|107|741,043|16.8%|
|2011|17|107|980,204|22.73%|

Question: how many more seats were available in 1975 than 1963?
Answer: 17